I do it like Tony. Since my side purflings are usually black and white fiber, the sheets of this stuff that are available in various thicknesses from LMI are useful.
The heel cap is always the last piece to get glued on my guitars. After the neck is fully fitted, with a bit of extra length in the heel, I mark the sides of the heel where I want it to end up so the purflings align, and trim it on a disc sander. First come close, then take off small increments. You could plane it, but it's hard to hand sand such a small area with a block and keep it flat.
I glue the "purfling" lams, and then the cap. All a little oversize. Then trim them to the heel.
I don't understand why the method of joining the neck affects this at all. I've done it with both dovetail and bolt joints.
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Howard Klepper
http://www.klepperguitars.comWhen all else fails, clean the shop.